Deep carbon cycle constrained by carbonate solubility.
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Farsang, S., Louvel, M., Zhao, C., Mezouar, M., Rosa, A. D., Widmer, R. N., Feng, X., et al. (2021). Deep carbon cycle constrained by carbonate solubility.. Nature communications, 12 (1)https://doi.org/10.1038/s41467-021-24533-7
Earth's deep carbon cycle affects atmospheric CO<sub>2</sub>, climate, and habitability. Owing to the extreme solubility of CaCO<sub>3</sub>, aqueous fluids released from the subducting slab could extract all carbon from the slab. However, recycling efficiency is estimated at only around 40%. Data from carbonate inclusions, petrology, and Mg isotope systematics indicate Ca<sup>2+</sup> in carbonates is replaced by Mg<sup>2+</sup> and other cations during subduction. Here we determined the solubility of dolomite [CaMg(CO<sub>3</sub>)<sub>2</sub>] and rhodochrosite (MnCO<sub>3</sub>), and put an upper limit on that of magnesite (MgCO<sub>3</sub>) under subduction zone conditions. Solubility decreases at least two orders of magnitude as carbonates become Mg-rich. This decreased solubility, coupled with heterogeneity of carbon and water subduction, may explain discrepancies in carbon recycling estimates. Over a range of slab settings, we find aqueous dissolution responsible for mobilizing 10 to 92% of slab carbon. Globally, aqueous fluids mobilise [Formula: see text]% ([Formula: see text] Mt/yr) of subducted carbon from subducting slabs.
RCUK | Natural Environment Research Council (NERC) (NE/L002507/1)
External DOI: https://doi.org/10.1038/s41467-021-24533-7
This record's URL: https://www.repository.cam.ac.uk/handle/1810/326797
Attribution 4.0 International
Licence URL: https://creativecommons.org/licenses/by/4.0/